Auton Soldier, and Felidar Guardian

Prerequisites

• Auton Soldier in hand
• Felidar Guardian on the battlefield

Steps

1. Cast Auton Soldier by paying its mana cost, choosing to have it enter the battlefield as a copy of Felidar Guardian When Auton Soldier enters the battlefield, it triggers, blinking Felidar Guardian
2. When Felidar Guardian enters the battlefield, it triggers, blinking Auton Soldier
3. Choose to have Auton Soldier enter the battlefield as a copy of Felidar Guardian
4. Repeat from step 2

Results

• Infinite LTB
• Infinite ETB